1. Field of the Invention
The present invention relates to a pigment-based yellow ink composition, particularly a yellow ink composition suitable for ink jet recording.
2. Background Art
Ink jet recording is a printing method wherein droplets of an ink composition are ejected and deposited onto a recording medium, such as paper, to conduct printing. This method has a feature that an image having high resolution and quality can be printed at a high speed by means of a relatively inexpensive apparatus. In general, the ink composition used in the ink jet recording comprises water as a main component and, added thereto, a colorant and a wetting agent, such as glycerin, for preventing clogging and other purposes. Water-soluble dyes, by virtue of high chroma of the colorant, abundance in types of usable colorants, solubility in water and other advantageous properties, have been extensively used as the colorant in the ink composition for ink jet recording. The dyes, however, are essentially soluble in water, and hence are often poor in waterfastness and other various properties.
Pigments, as compared with the dyes, have superior waterfastness. This has recently led to studies on utilization of pigments as a colorant in the ink composition for ink jet recording from the viewpoint of improving the waterfastness of the printed image. However, among various pigments, only limited pigments can exhibit color reproduction and other properties comparable to dyes. For yellow pigments, use of C.I. Pigment Yellow 74 can be expected by virtue of high color reproduction.
C.I. Pigment Yellow 74, however, often has poor lightfastness that is a disadvantageous property commonly observed in yellow pigments, and, hence, techniques for improving the lightfastness of this pigment have been desired in the art.